Establishing the relative accuracy of three new definitions of the adult respiratory distress syndrome

Acute Respiratory Distress Syndrome Phenotypes

The acute respiratory distress syndrome (ARDS) phenotype was first described over 50 years ago and since that time significant progress has been made in understanding the biologic processes underlying the syndrome. Despite this improved understanding, no pharmacologic therapies aimed at the underlying biology have been proven effective in ARDS. Increasingly, ARDS has been recognized as a heterogeneous syndrome characterized by subphenotypes with distinct clinical, radiographic, and biologic differences, distinct outcomes, and potentially distinct responses to therapy. The Berlin Definition of ARDS specifies three severity classifications: mild, moderate, and severe based on the PaO₂ to FiO₂ ratio. Two randomized controlled trials have demonstrated a potential benefit to prone positioning and neuromuscular blockade in moderate to severe phenotypes of ARDS only. Precipitating risk factor, direct versus indirect lung injury, and timing of ARDS onset can determine other clinical phenotypes of ARDS after admission. Radiographic phenotypes of ARDS have been described based on a diffuse versus focal pattern of infiltrates on chest imaging. Finally and most promisingly, biologic subphenotypes or endotypes have increasingly been identified using plasma biomarkers, genetics, and unbiased approaches such as latent class analysis. The potential of precision medicine lies in identifying novel therapeutics aimed at ARDS biology and the subpopulation within ARDS most likely to respond. In this review, we discuss the challenges and approaches to subphenotype ARDS into clinical, radiologic, severity, and biologic phenotypes with an eye toward the future of precision medicine in critical care.

Fifty Years of Research in ARDS. The Epidemiology of Acute Respiratory Distress Syndrome. A 50th Birthday Review

Since its first description 50 years ago, no other intensive care syndrome has been as extensively studied as acute respiratory distress syndrome (ARDS). Despite this extensive body of research, many basic epidemiologic questions remain unsolved. The lack of gold standard tests jeopardizes accurate diagnosis and translational research. Wide variation in the population incidence has been reported, making even simple estimates of the burden of disease problematic. Despite these limitations, there has been an increase in the understanding of pathophysiology and important risk factors both for the development of ARDS and for important patient-centered outcomes like mortality. In this Critical Care Perspective, we discuss the historical context of ARDS description and attempts at its definition. We highlight the epidemiologic challenges of studying ARDS, as well as other intensive care syndromes, and propose solutions to address them. We update the current knowledge of ARDS trends in incidence and mortality, risk factors, and recently described endotypes.

What is Acute Respiratory Distress Syndrome?

Acute respiratory distress syndrome (ARDS) is a form of acute lung injury which usually occurs within 24 hours of a major illness or injury. Unfortunately a clear definition of ARDS does not presently exist, and the variability in the diagnostic criteria may impact on the results of clinical trials for ARDS and our understanding of the epidemiology and pathogenesis of this syndrome. In this article the history of ARDS is reviewed and a few of the definitions that have evolved over wtime are explored in depth. In addition, several controversies with these existing defiitions are discussed.

Temporal evolution of acute respiratory distress syndrome definitions

OBJECTIVE

to review the evolution of acute respiratory distress syndrome (ARDS) definitions and present the current definition for the syndrome.

DATA SOURCE

a literature review and selection of the most relevant articles on ARDS definitions was performed using the MEDLINE®/PubMed® Resource Guide database (last ten years), in addition to including the most important articles (classic articles) that described the disease evolution.

DATA SYNTHESIS

the review included the following subjects: introduction; importance of definition; description of the first diagnostic criterion and subsequently used definitions, such as acute lung injury score; definition by the American-European Consensus Conference, and its limitations; description of the definition by Delphi, and its problems; accuracy of the aforementioned definitions; description of most recent definition (the Berlin definition), and its limitations; and practical importance of the new definition.

CONCLUSIONS

ARDS is a serious disease that remains an ongoing diagnostic and therapeutic challenge. The evolution of definitions used to describe the disease shows that studies are needed to validate the current definition, especially in pediatrics, where the data are very scarce.

Scutellarin protects against lipopolysaccharide-induced acute lung injury via inhibition of NF-kappaB activation in mice

This paper investigates the effect of natural scutellarin on acute lung injury (ALI) induced by Escherichia coli endotoxin lipopolysaccharide (LPS) in mice and its mechanism of action. Mouse ALI was induced by the injection of LPS (15 mg/kg) via the tail vein, and mice were intraperitoneally injected with 50 and 25 mg/kg of scutellarin before the LPS injection. The lung index, serum NO2(-)/NO3(-), and tumor necrosis factor-alpha (TNF-alpha) levels were determined using kits. The lung lesions were examined by light microscope. The mRNA levels of TNF-alpha, inducible nitric oxide synthase (iNOS), and FasL in pulmonary tissues were detected by RT-PCR. c-Fos, c-Jun, IkappaB, and iNOS proteins were detected by the western blotting method. Pretreatment with 25 and 50 mg/kg of scutellarin significantly reduced lung injury induced by LPS, which expressed in the decrease in lung morphological lesions, serum NO2(-)/NO3(-), TNF-alpha levels, lactate dehydrogenase release, and total protein in the lavage fluid of bronchoalveolar of the lung. The mRNA level of TNF-alpha, iNOS, the protein content of c-Fos, iNOS, and the activation of NF-kappaB in pulmonary tissues were all inhibited, while the lung glutathione level increased. In conclusion, scutellarin has protective action against LPS-induced lung damage in mice, and its underlying mechanism might be the inhibition of IkappaB alpha degradation and the expression of TNF-alpha mRNA.

Better infrastructure for critical care trials: nomenclature, etymology, and informatics

OBJECTIVE

The goals of this review article are to review the importance and value of standardized definitions in clinical research, as well as to propose the necessary tools and infrastructure needed to advance nosology and medial taxonomy to improve the quality of clinical trials in the field of critical care.

DATA SOURCES

We searched MEDLINE for relevant articles, reviewed those selected and their reference lists, and consulted personal files for relevant information.

DATA SYNTHESIS

When the pathobiology of diseases is well understood, standard disease definitions can be extremely specific and precise; however, when the pathobiology of the disease is less well understood or more complex, biological markers may not be diagnostically useful or even available. In these cases, syndromic definitions effectively classify and group illnesses with similar symptoms and clinical signs. There is no clear gold standard for the diagnosis of many clinical entities in the intensive care unit, including notably both acute respiratory distress syndrome and sepsis. There are several types of consensus methods that can be used to explicate the judgmental approach that is often needed in these cases, including interactive or consensus groups, the nominal group technique, and the Delphi technique. Ideally, the definition development process will create clear and unambiguous language in which each definition accurately reflects the current understanding of the disease state.

CONCLUSIONS

The development, implementation, evaluation, revision, and reevaluation of standardized definitions are keys for advancing the quality of clinical trials in the critical care arena.

Acute respiratory distress syndrome 40 years later: time to revisit its definition

OBJECTIVE

Acute respiratory distress syndrome is a common disorder associated with significant mortality and morbidity. The aim of this article is to critically evaluate the definition of acute respiratory distress syndrome and examine the impact the definition has on clinical practice and research.

DATA SOURCES

Articles from a MEDLINE search (1950 to August 2007) using the Medical Subject Heading respiratory distress syndrome, adult, diagnosis, limited to the English language and human subjects, their relevant bibliographies, and personal collections, were reviewed.

DATA SYNTHESIS

The definition of acute respiratory distress syndrome is important to researchers, clinicians, and administrators alike. It has evolved significantly over the last 40 years, culminating in the American-European Consensus Conference definition, which was published in 1994. Although the American-European Consensus Conference definition is widely used, it has some important limitations that may impact on the conduct of clinical research, on resource allocation, and ultimately on the bedside management of such patients. These limitations stem partially from the fact that as defined, acute respiratory distress syndrome is a heterogeneous entity and also involve the reliability and validity of the criteria used in the definition. This article critically evaluates the American-European Consensus Conference definition and its limitations. Importantly, it highlights how these limitations may contribute to clinical trials that have failed to detect a potential true treatment effect. Finally, recommendations are made that could be considered in future definition modifications with an emphasis on the significance of accurately identifying the target population in future trials and subsequently in clinical care.

CONCLUSION

How acute respiratory distress syndrome is defined has a significant impact on the results of randomized, controlled trials and epidemiologic studies. Changes to the current American-European Consensus Conference definition are likely to have an important role in advancing the understanding and management of acute respiratory distress syndrome.

[Sedation an acute respiratory distress syndrome]

AIM

To assess the role of sedation and myorelaxant agents in acute respiratory distress syndrome (ARDS) and to propose an updated management according to recent literature. EXTRACTION OF DATA: From Medline and Cochrane database of English and French language articles. Keywords were: acute respiratory distress syndrome, acute lung injury, general anaesthetics, inhalation, intravenous anaesthetics and intensive care. Selection of original articles, reviews and expert reports. Case reports have been included.

TOPIC

ARDS is a clinical picture in which respiratory constraints are major because of hypoxemia. To insure correct haematosis, mechanical ventilation has to be considered. It constitutes, then, the most frequent indication of sedation in the intensive care unit. The objectives are to help the ventilation of lungs and to improve gas exchange, by controlling agitation, fight against ventilation and to reduce mechanical ventilation associated injuries. In this situation, use of myorelaxant agents is aimed at facilitating synchronization of the patient with his/her ventilator and serves to improve oxygenation during the early inflammatory phase of ARDS. Several mechanisms may enflame this improvement of oxygenation. One of the most probable effect on optimization is the possibility of optimize protective ventilation at the cares phase of ARDS and to reduce mechanical ventilation-associated injuries.

CONCLUSION

With regard to benefits and inconvenient, sedation is considered as a treatment of ARDS. Its goals are the well being of patient and his/her adaptation to ventilator, but also the prevention on mechanical ventilation associated injuries. Hence, most authors suggest using a deep sedation at the early phase of ARDS. In this contact, use of myorelaxant agent is an intersecting adjuvant if sedation is not enough. The benefit is terms of survival and outcome remains to show.

Epidemiology of acute lung injury and acute respiratory distress syndrome in The Netherlands: A survey

BACKGROUND

The characteristics, incidence and risk factors for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) may depend on definitions and geography.

METHODS

A prospective, 3-day point-prevalence study was performed by a survey of all intensive care units (ICU) in the Netherlands (n=96). Thirty-six ICU's responded (37%), reporting on 266 patients, of whom 151 were mechanically ventilated. The questionnaire included criteria and potential risk factors for ALI/ARDS, according to the North American-European Consensus Conference (NAECC) or the lung injury score (LIS>or=2.5).

RESULTS

Agreement between definitions was fair (kappa 0.31-0.42, P=0.001). ALI/ARDS was characterized, regardless of definition, by radiographic densities, low oxygenation ratios, high inspiratory O(2) and airway pressure requirements. Depending on definitions, ALI and ARDS accounted for about 12-33% and 7-9% of ICU admissions per year, respectively, constituting 21-58% (ALI) and 13-16% (ARDS) of all mechanically ventilated patients. The annual incidences of ALI and ARDS are 29.3 (95%CI 18.4-40.1) and 24.0 (95%CI 14.2-33.8) by NAECC, respectively, and are, respectively, 83.6 (95%CI 65.3-101.9) and 20.9 (95%CI 11.7-30.1) by LIS per 100,000. Risk factors for ALI/ARDS were aspiration, pneumonia, sepsis and chronic alcohol abuse (the latter only by NAECC).

CONCLUSION

The effect of definitions of ALI/ARDS on mechanical ventilation in the Netherlands is small. Nevertheless, the incidence of ALI/ARDS may be higher than in other European countries but lower than in the USA, and the incidence of ALI by LIS may overestimate compared to that by NAECC. Aspiration, pneumonia, sepsis and chronic alcohol abuse are major risk factors, largely independent of definitions.

Comparison of the SpO2/FIO2 ratio and the PaO2/FIO2 ratio in patients with acute lung injury or ARDS

BACKGROUND

The diagnostic criteria for acute lung injury (ALI) and ARDS utilize the Pao(2)/fraction of inspired oxygen (Fio(2)) [P/F] ratio measured by arterial blood gas analysis to assess the degree of hypoxemia. We hypothesized that the pulse oximetric saturation (Spo(2))/Fio(2) (S/F) ratio can be substituted for the P/F ratio in assessing the oxygenation criterion of ALI.

METHODS

Corresponding measurements of Spo(2) (values </= 97%) and Pao(2) from patients enrolled in the ARDS Network trial of a lower tidal volume ventilator strategy (n = 672) were compared to determine the relationship between S/F and P/F. S/F threshold values correlating with P/F ratios of 200 (ARDS) and 300 (ALI) were determined. Similar measurements from patients enrolled in the ARDS Network trial of lower vs higher positive end-expiratory pressure (n = 402) were utilized for validation.

RESULTS

In the derivation data set (2,613 measurements), the relationship between S/F and P/F was described by the following equation: S/F = 64 + 0.84 x (P/F) [p < 0.0001; r = 0.89). An S/F ratio of 235 corresponded with a P/F ratio of 200, while an S/F ratio of 315 corresponded with a P/F ratio of 300. The validation database (2,031 measurements) produced a similar linear relationship. The S/F ratio threshold values of 235 and 315 resulted in 85% sensitivity with 85% specificity and 91% sensitivity with 56% specificity, respectively, for P/F ratios of 200 and 300.

CONCLUSION

S/F ratios correlate with P/F ratios. S/F ratios of 235 and 315 correlate with P/F ratios of 200 and 300, respectively, for diagnosing and following up patients with ALI and ARDS.

Epidemiology and Outcomes of Acute Lung Injury

Acute lung injury (ALI) and its presentation with more severe hypoxemia, the ARDS, is a challenging entity for clinical investigation because, like many critical illness syndromes, it lacks an accepted diagnostic test and relies on a constellation of clinical findings for diagnosis. Despite these barriers, there have been important advances in the clinical and population epidemiology of ALI. This article will review recent studies of the incidence, diagnosis, etiologic and prognostic factors, relevant disease subsets, mortality, and long-term outcomes of ALI. A detailed understanding of the epidemiology and outcomes of ALI is essential for future research on mechanisms of both the acute presentation and long-term sequelae, for designing studies to identify genetic risk factors for developing ALI, and to develop strategies to treat or prevent the morbidity encountered by survivors.

Acute lung injury and the acute respiratory distress syndrome: challenges in clinical trial design

Despite significant advances in the understanding of the complex pathophysiology, only a limited number of new treatments for acute lung injury (ALI) have emerged in the last 2 decades. This article discusses some of the challenges that remain in conducting clinical research in patients who have ALI and acute respiratory distress syndrome. New definitions that incorporate prognostic measures and reduce patient heterogeneity will allow more efficient enrollment of patients. Delineating outcomes attributable to the lung injury will improve the power of studies to detect significant treatment effects. Future collaborative studies will be needed to investigate longer-term clinical outcomes.

Pathology of Acute Lung Injury and Acute Respiratory Distress Syndrome: A Clinical–Pathological Correlation

Clinical criteria cannot identify all patients who develop acute respiratory distress syndrome, which might indicate the need to develop new tools that improve reliability and diagnostic accuracy. Nevertheless, being conscious of the limitations of the American-European consensus conference criteria continues to be useful in clinical daily practice because these patients would benefit from treatments. This and other management strategies have been evaluated in patients who, fulfilling the clinical criteria of acute respiratory distress syndrome, could not have diffuse alveolar damage.

Evaluation of clinical criteria for the acute respiratory distress syndrome in pediatric patients

OBJECTIVE

The primary goal of this study was to evaluate the validity of the North American-European Consensus Committee (NAECC) definition for acute respiratory distress syndrome (ARDS) in pediatric patients. A secondary aim was to evaluate the threshold value for the PaO2/FiO2 ratio, used to determine which pediatric patients have ARDS.

DESIGN

Retrospective cohort study.

SETTING

Pediatric intensive care unit.

PATIENTS

Pediatric intensive care unit patients who required mechanical ventilation, died, and underwent autopsy between January 1, 1996, and December 31, 2002 (n = 34).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Clinical and chest radiograph information was collected retrospectively through chart review using a standardized data collection tool. Data included the criteria specified in the NAECC definition of ARDS and demographic information. We calculated the sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio of clinical diagnosis of ARDS compared with a pathologic diagnosis. The threshold value of PaO2/FiO2 was identified by plotting receiver operating characteristics curves and comparing the areas under the curves. The NAECC definition yielded a sensitivity of 80.7% (95% confidence interval 60-92%), specificity of 71.4% (95% confidence interval 30-95), positive predictive value of 91.3% (95% confidence interval 70-98), negative predictive value of 50.0% (95% confidence interval 20-78), and likelihood ratio of 2.82. A PaO2/FiO2 <150 had a slightly higher (but not significantly different) specificity for ARDS than a value >200 (71% vs. 86%, p = .15) without changing sensitivity.

CONCLUSIONS

Our study suggests the need for further research with larger number of children to identify an optimal Pao2/Fio2 threshold for identifying ARDS in this population.

Development of a clinical definition for acute respiratory distress syndrome using the Delphi technique

PURPOSE

The objective of this study is to describe the implementation of formal consensus techniques in the development of a clinical definition for acute respiratory distress syndrome.

MATERIALS AND METHODS

A Delphi consensus process was conducted using e-mail. Sixteen panelists who were both researchers and opinion leaders were systematically recruited. The Delphi technique was performed over 4 rounds on the background of an explicit definition framework. Item generation was performed in round 1, item reduction in rounds 2 and 3, and definition evaluation in round 4. Explicit consensus thresholds were used throughout.

RESULTS

Of the 16 panelists, 11 actually participated in developing a definition that met a priori consensus rules on the third iteration. New incorporations in the Delphi definition include the use of a standardized oxygenation assessment and the documentation of either a predisposing factor or decreased thoracic compliance. The panelists rated the Delphi definition as acceptable to highly acceptable (median score, 6; range, 5-7 on a 7-point Likert scale).

CONCLUSIONS

We conclude that it is feasible to consider using formal consensus in the development of future definitions of acute respiratory distress syndrome. Testing of sensibility, reliability, and validity are needed for this preliminary definition; these test results should be incorporated into future iterations of this definition.

Epidemiology of multiple organ dysfunction syndrome in critical surgical illness

Multiple organ dysfunction syndrome (MODS) is a major cause of morbidity and mortality in surgical intensive care units (SICUs). Multiple organ dysfunction syndrome remains the most important factor associated with mortality in the SICU. Illness severity scores such as the Acute Physiology and Chronic Health Evaluation-III (APACHE III) and the magnitude of the systemic inflammatory response syndrome (SIRS) at the time of SICU admission are useful in stratifying patients at risk for MODS and subsequent mortality. Assessment of key organ systems shows that mortality correlates with the overall severity of organ dysfunction and the number of involved organ systems, as well as to individual organs that fail. Despite the prognostic utility of SIRS/MODS, definitions of dysfunction of individual organs have shortcomings. The problem with quantitating MODS lies in the inability to adequately define organ dysfunction, especially of the gastrointestinal tract, liver, and central nervous system. Biological indicators of organ dysfunction may prove to be better markers for MODS in the future.

Extravascular lung water in patients with severe sepsis: a prospective cohort study

Introduction

Few investigations have prospectively examined extravascular lung water (EVLW) in patients with severe sepsis. We sought to determine whether EVLW may contribute to lung injury in these patients by quantifying the relationship of EVLW to parameters of lung injury, to determine the effects of chronic alcohol abuse on EVLW, and to determine whether EVLW may be a useful tool in the diagnosis of acute respiratory distress syndrome (ARDS).

Methods

The present prospective cohort study was conducted in consecutive patients with severe sepsis from a medical intensive care unit in an urban university teaching hospital. In each patient, transpulmonary thermodilution was used to measure cardiovascular hemodynamics and EVLW for 7 days via an arterial catheter placed within 72 hours of meeting criteria for severe sepsis.

Results

A total of 29 patients were studied. Twenty-five of the 29 patients (86%) were mechanically ventilated, 15 of the 29 patients (52%) developed ARDS, and overall 28-day mortality was 41%. Eight out of 14 patients (57%) with non-ARDS severe sepsis had high EVLW with significantly greater hypoxemia than did those patient with low EVLW (mean arterial oxygen tension/fractional inspired oxygen ratio 230.7 ± 36.1 mmHg versus 341.2 ± 92.8 mmHg; P < 0.001). Four out of 15 patients with severe sepsis with ARDS maintained a low EVLW and had better 28-day survival than did ARDS patients with high EVLW (100% versus 36%; P = 0.03). ARDS patients with a history of chronic alcohol abuse had greater EVLW than did nonalcoholic patients (19.9 ml/kg versus 8.7 ml/kg; P < 0.0001). The arterial oxygen tension/fractional inspired oxygen ratio, lung injury score, and chest radiograph scores correlated with EVLW (r² = 0.27, r² = 0.18, and r² = 0.28, respectively; all P < 0.0001).

Conclusions

More than half of the patients with severe sepsis but without ARDS had increased EVLW, possibly representing subclinical lung injury. Chronic alcohol abuse was associated with increased EVLW, whereas lower EVLW was associated with survival. EVLW correlated moderately with the severity of lung injury but did not account for all respiratory derangements. EVLW may improve both risk stratification and management of patients with severe sepsis.

Incidence of acute respiratory distress syndrome in German children and adolescents: A population-based study

OBJECTIVE

The objective of this study was to determine the epidemiology of acute respiratory distress syndrome (ARDS) in children and adolescents aged 1 mo to 18 yrs.

DESIGN

The authors conducted a population-based prospective multicenter survey from February 1 to 28,1997, June 1 to 30, 2001, and April 1 to 30, 2004.

SETTING

This study was conducted at 94 intensive care units (ICUs) in 1997, 92 ICUs in 2001 and 2004 in the district of Cologne, Germany with a population of 4.15 (1997), 4.28 (2001), and 4.35 million (2004), respectively. The survey was not confined to children's hospitals, but addressed all ICUs.

PATIENTS

This study consisted of children and adolescents aged 1 mo to 18 yrs. Term neonates and premature babies with a corrected age below 43 gestational weeks were excluded. ARDS was defined according to the consensus criteria (acute-onset pulmonary process of noncardiogenic origin, Pao(2)/FIo(2) ratio <200, bilateral alveolar infiltration in chest radiograph).

RESULTS

All ICUs at pediatric hospitals and all but seven adult ICUs collaborated. Incidence of ARDS was assessed as the number of patients entering ARDS criteria within the three study periods divided by the total population in this age group. During the study period, 12 pediatric patients were diagnosed as having ARDS. In five cases, onset was before the study period, representing a calculated prevalence of 5.5 x 10(-5) [3.1 x 10(-5); 9.6 x 10(-5)] cases per year and an incidence of 3. 2 x 10(-5) [1.5 x 10(-5); 6.6 x 10(-5)] cases per year in the age group under investigation.

CONCLUSION

This is the first population-based evaluation of the incidence of ARDS in the pediatric age group. It shows that the incidence of ARDS in this age group is low. This makes randomized studies on pediatric ARDS aiming on the end point "outcome" nearly impossible.

Acute lung injury and acute respiratory distress syndrome

Acute lung injury and acute respiratory distress syndrome are an important challenge for pediatric intensive care units. These disorders are characterized by a significant inflammatory response to a local (pulmonary) or remote (systemic) insult resulting in injury to alveolar epithelial and endothelial barriers of the lung, acute inflammation and protein rich pulmonary edema. The reported rates in children vary from 8.5 to 16 cases / 1000 pediatric intensive care unit (PICU) admissions. The pathological features of ARDS are described as passing through three overlapping phases - an inflammatory or exudative phase (0-7 days), a proliferative phase (7-21 days) and lastly a fibrotic phase (from day 10). The treatment of ARDS rests on good supportive care and control of initiating cause. The goal of ventilating patients with ALI/ARDS should be to maintain adequate gas exchange with minimal ventilator induced lung injury. This can be achieved by use of optimum PEEP, low tidal volume and appropriate FiO2. High frequency ventilation can improve oxygenation but does affect the outcomes. Prone positioning is a useful strategy to improve oxygenation. Pharmacological strategies have not made any significant impact on the outcomes. Preliminary data suggests some role for use of corticosteroids in non-resolving ARDS. The mortality rates have declined over the last decade chiefly due to the advances in supporting critically ill patients.

Impact of positive end-expiratory pressure on the definition of acute respiratory distress syndrome

OBJECTIVE

We examined whether PEEP during the first hours of ARDS can induce such a change in oxygenation that could mask fulfillment of the AECC criteria of a PaO(2)/FIO(2) </= 200 essential for ARDS diagnosis.

DESIGN AND SETTING

Observational, prospective cohort in two medical-surgical ICU in teaching hospitals.

PATIENTS

48 consecutive patients who met AECC criteria of ARDS on 0 PEEP (ZEEP) at the moment of diagnosis.

MEASUREMENTS AND RESULTS

PaO(2)/FIO(2) and lung mechanics were recorded on admission (0 h) to the ICU on ZEEP, and after 6, 12, and 24 h on PEEP levels selected by attending physicians. Lung Injury Score (LIS) was calculated at 0 and 24 h. PaO(2)/FIO(2) rose significantly from 121+/-45 on ZEEP at 0 h, to 234+/-85 on PEEP of 12.8+/-3.7 cmH(2)O after 24 h. LIS did not change significantly (2.34+/-0.53 vs. 2.42+/-0.62). These variables behaved similarly in pulmonary and extrapulmonary ARDS, and in survivors and nonsurvivors. After 24 h only 18 patients (38%) still had a PaO(2)/FIO(2) of 200 or lower. Their mortality was similar to that in the remaining patients (61% vs. 53%).

CONCLUSIONS

The use of PEEP improved oxygenation such that one-half of patients after 6 h, and most after 24 h did not fulfill AECC hypoxemia criteria of ARDS. However, LIS remained stable in the overall series. These results suggest that PEEP level should be taken into consideration for ARDS diagnosis.

Lung injury severity scoring in the era of lung protective mechanical ventilation: the PaO2/FIO2 ratio

BACKGROUND

Lung protective ventilatory strategies using low tidal volume and high positive end-expiratory pressure (PEEP) have become standard practice. Such strategies, however, may invalidate measurement of lung injury severity by traditional methods that are based on plain chest radiograph findings, oxygenation, minute ventilation, lung compliance, and PEEP level, such as the Murray lung injury score (LIS). Many of these criteria are potentially therapy dependent and may change with different ventilatory strategies. The purpose of this study was to determine whether measurement of lung injury severity based simply on oxygenation criteria (PaO(2)/FIO(2)) was as accurate as the Murray LIS currently used in multiple organ failure (MOF) scoring.

METHODS

Since 1992, trauma patients at high risk for developing MOF have been prospectively identified and MOF scores calculated daily. Pulmonary dysfunction is graded from 0 to 3 on the basis of a modified Murray LIS incorporating the aforementioned parameters. Lung injury severity was redefined using the PaO(2)/FIO(2) (P/F score): Grade 0 = >250; 1 = 175 to 250; 2 = 100 to 174; and 3 = <100. The maximum (worst) score using each was compared using logistic regression and receiver operating characteristic curve analysis.

RESULTS

Five hundred thirty-nine trauma patients had lung injury severity assessed using both LIS and P/F score. The mean P/F score was over twice the mean LIS (1.9 +/-.04 vs. 0.9+/-.04, p < 0.0001). In 28% of patients, the LIS and P/F score were identical, whereas in 71%, the P/F score was greater than the LIS. Both scores were significant predictors of mortality; however, receiver operating characteristic curve analysis showed that the P/F score was superior in predicting mortality (area under the curve, 0.74+/-.03 vs. 0.67+/-.04).

CONCLUSION

The P/F score is a simple method of quantifying lung injury severity in trauma patients that better predicts mortality compared with the more complicated modified Murray lung injury score currently in use. The P/F score should replace more complex and potentially therapy-dependent scores.

Low stretch ventilation strategy in acute respiratory distress syndrome: eight years of clinical experience in a single center

CONTEXT

In recent years, protective ventilation with airway pressure limitation has constituted a major advance in acute respiratory distress syndrome treatment and has led to a substantial improvement in prognosis. With this therapeutic rationale, one may even question nowadays whether the severity of respiratory failure still influences mortality.

OBJECTIVE

To determine whether the severity of respiratory failure, scored according to the usual criteria, still influences mortality in acute respiratory distress syndrome patients when a low stretch ventilation was used and to assess the impact on mortality of other nonpulmonary organ dysfunction, particularly circulatory failure.

DESIGN AND SETTING

A retrospective study conducted in the medical intensive care unit of a French university hospital from October 1993 to December 2001. PATIENTS A total of 150 acute respiratory distress syndrome patients who were administered uniform protective ventilation with a limited plateau pressure (<30 cm H2O), a low positive end-expiratory pressure (<10 cm H2O), and the same strategy concerning hemodynamic support and dialysis when required.

MAIN OUTCOME AND MEASURES

Mean age, general severity index (Simplified Acute Physiologic Score II), number of associated organ failures (Logistic Organ Dysfunction Score), respiratory severity indices (Pao2/Fio2, Lung Injury Severity Score), and severity of initial circulatory failure (circulatory failure present at admission or that developed during the first 48 hrs) were compared, according to recovery or death, and evaluated by a logistic regression model, which allows simultaneous control of multiple factors.

RESULTS

The average mortality rate for the whole group was 38%, with 93 patients recovering after an average duration of mechanical ventilation of 18 +/- 13 days. The major factor significantly and independently associated with probability of dying was the severity of circulatory failure (p =.0001, odds ratio = 10.17). Patients free from initial circulatory failure (39 patients) had a 95% recovery rate.

CONCLUSION

With our low stretch strategy, the severity of circulatory failure was the main determinant of acute respiratory distress syndrome prognosis. Patients with isolated respiratory failure during the first 48 hrs of respiratory support have an excellent chance of recovery when treated with protective ventilation associated with a low positive end-expiratory pressure.

Race and gender differences in acute respiratory distress syndrome deaths in the United States: an analysis of multiple-cause mortality data (1979- 1996)

OBJECTIVE

Acute respiratory distress syndrome (ARDS) is a devastating clinical disorder that affects critically ill patients with a wide variety of underlying illnesses. Presently, there is limited population-based information concerning both the impact of ARDS on mortality, and the effects of race and gender on national ARDS mortality rates. In this study, we have attempted to evaluate trends over an 18-yr period in deaths associated with ARDS in the United States.

DESIGN

Case series.

PATIENTS

The Multiple-Cause Mortality Files compiled by the National Center for Health Statistics from 1979-1996 contains information on 38,263,780 decedents. We identified 333,004 decedents who had ARDS.

MEASUREMENTS AND MAIN RESULTS

We calculated age-adjusted annual ARDS mortality rates. The annual age-adjusted mortality rate for ARDS initially increased from 1979 (5.0 deaths per 100,000 individuals) to 1993 (8.1 deaths per 100,000 individuals). From 1993 to 1996, the mortality rate for ARDS decreased significantly to 7.4 deaths per 100,000 individuals. Annual ARDS mortality rates have been continuously higher for men when compared with women and for African-Americans when compared with white decedents and decedents of other racial backgrounds. When decedents were stratified by race and gender, African-American men had the highest ARDS mortality rates in comparison to all other subgroups (mean annual mortality rate of 12.8 deaths per 100,000 African-American men).

CONCLUSIONS

Although the annual ARDS mortality rate is slowly declining in the United States, significant race and gender differences in ARDS mortality exist.

The pulmonary physician in critical care. 5: Acute lung injury and the acute respiratory distress syndrome: definitions and epidemiology

An understanding of the epidemiology of ALI/ARDS and the effects of treatment have been hampered by the lack of a uniform definition of the syndrome. Various definitions have been proposed, and these are reviewed with particular attention to how changes in definition have affected our understanding of the natural history and treatment options for the condition.

Pulmonary dead-space fraction as a risk factor for death in the acute respiratory distress syndrome

BACKGROUND

No single pulmonary-specific variable, including the severity of hypoxemia, has been found to predict the risk of death independently when measured early in the course of the acute respiratory distress syndrome. Because an increase in the pulmonary dead-space fraction has been described in observational studies of the syndrome, we systematically measured the dead-space fraction early in the course of the illness and evaluated its potential association with the risk of death.

METHODS

The dead-space fraction was prospectively measured in 179 intubated patients, a mean (+/-SD) of 10.9+/-7.4 hours after the acute respiratory distress syndrome had developed. Additional clinical and physiological variables were analyzed with the use of multiple logistic regression. The study outcome was mortality before hospital discharge.

RESULTS

The mean dead-space fraction was markedly elevated (0.58+/-0.09) early in the course of the acute respiratory distress syndrome and was higher among patients who died than among those who survived (0.63+/-0.10 vs. 0.54+/-0.09, P<0.001). The dead-space fraction was an independent risk factor for death: for every 0.05 increase, the odds of death increased by 45 percent (odds ratio, 1.45; 95 percent confidence interval, 1.15 to 1.83; P=0.002). The only other independent predictors of an increased risk of death were the Simplified Acute Physiology Score II, an indicator of the severity of illness (odds ratio, 1.06; 95 percent confidence interval, 1.03 to 1.08; P<0.001) and quasistatic respiratory compliance (odds ratio, 1.06; 95 percent confidence interval, 1.01 to 1.10; P=0.01).

CONCLUSIONS

Increased dead-space fraction is a feature of the early phase of the acute respiratory distress syndrome. Elevated values are associated with an increased risk of death.

Elevated plasma surfactant protein-B predicts development of acute respiratory distress syndrome in patients with acute respiratory failure

Surfactant protein-B is a lung specific protein secreted into the air spaces by pulmonary epithelial type II cells that leaks into the bloodstream in increased amounts in patients with ARDS. To test whether elevated plasma levels of surfactant protein-B would predict the development of ARDS in patients with acute hypoxemic respiratory failure, plasma and lung injury scores were collected at study entry and daily thereafter for 3 d from 54 patients admitted to our intensive care unit. ARDS was defined as a new bilateral infiltrate on chest radiograph and a lung injury score > or = 2.5. Twenty patients developed ARDS, of whom seven died. Although the initial lung injury score was not predictive of ARDS, the initial plasma surfactant protein-B was predictive (area under the curve = 0.77 [0.63 to 0.90], nonparametric receiver-operating characteristic analysis). In this cohort, plasma surfactant protein-B was particularly predictive of ARDS when applied to patients suffering a direct lung insult (area under the curve = 0.87 [0.72 to 1.02]), with a sensitivity of 85% (95% CI: 55 to 98%) and specificity of 78% (40 to 97%) at a cutoff of 4,994 ng/ml.

Adult respiratory distress syndrome among blunt and penetrating trauma patients: demographics, mortality, and resource utilization over 8 years

PURPOSE

The purpose of this study was to compare demographics, resources used, and mortality rates among a subset of trauma patients (blunt versus penetrating) who developed adult respiratory distress syndrome (ARDS) and over two time periods, 8 years apart.

PATIENTS AND METHODS

This retrospective observational study was based on an analysis of the computerized Trauma Registry of the Shock Trauma Center of the University of Maryland Medical Systems. All trauma patients with ARDS admitted to a 48-bed trauma intensive care unit (ICU) at a Level I Trauma Center during two time periods of 3 consecutive years each were considered: from January 1, 1985, to December 31, 1987 (G1), and January 1, 1993, to December 31, 1995 (G2). Data were collected in the two time periods on demographics, severity (Revised Trauma Score), injury-admission delay time, first 24-hour transfusion fluids and blood, septic and organ system failure complications, life-support techniques, ICU mortality, and length of stay (LOS). The independent variables were the age, type of trauma, severity scores, transport time, fluid therapy, infectious and organ system failure complications, and life-support techniques. The dependent variable was ICU mortality.

RESULTS

A total of 1,108 patients satisfied the entry criteria, 486 in period G1 and 552 in period G2; 929 (89.5%) suffered blunt trauma and 109 (10.5%) penetrating trauma. Mean age was lower for the penetrating trauma populations. There were no significant differences in ICU mortality between the blunt and penetrating trauma patients with ARDS. A significant decrease in ICU mortality was observed between the time periods studied among both blunt (29.5% vs. 21.7%, P <.001) and penetrating trauma patients (25.7% vs. 18.9%, P <.001). A similar rate of renal, hematologic, and cardiovascular organ system failure was observed for both blunt and penetrating trauma patients. Resource utilization measured by ICU LOS and time on mechanical ventilation was also similar in the two groups. The multivariate analysis showed that ICU mortality was related to age, RTS-measured severity, and time period (G1 mortality 1.68-fold that in G2). Renal and hematologic failures entered a second analysis, replacing the time period variable (G2).

CONCLUSIONS

ARDS in patients with blunt and penetrating trauma showed similar trends in ICU mortality, complications, and resource utilization. The ARDS mortality rate decreased over the time period studied in both blunt and penetrating trauma.

A 9-year, single-institution, retrospective review of death rate and prognostic factors in adult respiratory distress syndrome

OBJECTIVE

To evaluate, at a single institution, the adult respiratory distress syndrome (ARDS) death rate in critically ill ventilated surgical/trauma patients and to identify the factors predicting death in these patients.

SUMMARY BACKGROUND DATA

The prognostic features affecting mortality at the onset of ARDS have not been clearly defined. Defining rare characteristics would be valuable because it would allow for better stratification of patients in clinical trials and more appropriate utilization of constrained resources in ICU environments.

METHODS

A retrospective analysis of 980 ventilated surgical and trauma intensive care unit patients from January 1990 to December 1998 was performed at Rhode Island Hospital. One hundred eleven adult intensive care unit patients with ARDS were identified using the criteria of Lung Injury Score more than 2.50 and the definition from the American-European Consensus Conference. Slightly more than half were trauma patients, 57% were men, and the median age was 59 years. The overall death rate was 52%. Patients were segregated by admission date to the intensive care unit (before or after January 1, 1995). Severity of illness was measured by the Revised Trauma Score for trauma patients and the Acute Physiology and Chronic Health Evaluation III for surgical patients. The Multiple Organ Dysfunction Score was determined on the day of onset of ARDS for all patients. Other recorded variables were age, sex, intensive care unit length of stay, length and mode of ventilation, presence or absence of tracheostomy, ventilation variables of peak and mean airway pressures, lung injury scores, elective versus emergency surgery, and presence or absence of pneumonia.

RESULTS

There was a significant decrease in the ARDS death rate from the period 1990 to 1994 to the period 1995 to 1998. The major reason for the decline was a reduction in the posttraumatic ARDS death rate. Lung-protective ventilation strategies were used more frequently in the second period than in the first, and the death rate was significantly decreased in trauma patients in the second period when lung-protective ventilation modes were used. Predictors of death at the onset of ARDS were advanced age, Multiple Organ Dysfunction Score of 8 or more, and Lung Injury Score of 2.76 or more.

CONCLUSION

In this single-institution series, the death rate from ARDS declined from 1990 to 1998, primarily in posttraumatic patients, and the decrease is related to the use of lung-protective ventilation strategies. Based on this patient population, the authors developed a statistical model to evaluate important prognostic indicators (advanced age, organ system and pulmonary dysfunction measurements) at the onset of ARDS.

Acute respiratory distress syndrome as a major clinical manifestation of thrombotic thrombocytopenic purpura

BACKGROUND

Although the classical triad of thrombocytopenia, microangiopathic hemolytic anemia, and neurological changes has been well recognized, thrombotic thrombocytopenic purpura (TTP) sometimes presents with atypical clinical features. Some cases of acute respiratory distress syndrome (ARDS) were suspected to be a manifestation of TTP.

METHODS

We examined retrospectively the medical records of patients with known TTP from 1981 to 1998. The patients who developed ARDS simultaneously with TTP were identified. Clinical, laboratory, and other pertinent data were reviewed; the clinical outcome was documented.

RESULTS

Seven out of 56 patients with an established diagnosis of TTP were identified as having ARDS. All 7 patients had progressive dyspnea, persistent hypoxemia with diffuse pulmonary infiltrates, and no evidence of localized pneumonia, pulmonary emboli, congestive heart failure, or other identifiable lung diseases. In addition to ARDS, 4 patients developed progressive neurological (mental) changes, 3 developed fever, and 2 developed renal failure. Six patients were treated with ventilatory support in the ICU. Upon establishing the diagnosis of TTP, 6 patients were treated with exchange plasmapheresis (EP) and 1 patient with an infusion of fresh frozen plasma. Within 2 days of initiation of EP, 4 patients showed marked respiratory improvement; shortly thereafter, mechanical ventilation was ended. Complete and long-lasting remission was achieved in all 4 patients. Three patients died because of delayed diagnosis and untimely employment of EP.

CONCLUSION

Life-threatening ARDS can be associated with TTP. It is recommended that all patients with ARDS and unexplained thrombocytopenia be evaluated for unrecognized TTP. Early recognition of ARDS associated with TTP and timely EP is critical to a favorable outcome.

Agreement between alternative classifications of acute respiratory distress syndrome

To examine the agreement between two classifications of acute respiratory distress syndrome (ARDS) that are used interchangeably in clinical practice and clinical research, we classified 118 patients taking part in a randomized trial with respect to the presence of ARDS using the North American-European Consensus Committee (NAECC) and the Lung Injury Severity Score (LISS) criteria. The incidence of ARDS using NAECC criteria was 55.1% (95% confidence interval, 46.1% to 64.1%), and using the LISS criteria 61.9% (95% confidence interval, 53.1% to 70.6%). The p value on the difference between these proportions was 0.07. Raw agreement, chance-corrected agreement (kappa), and chance-independent agreement (phi) on the study occurrence of ARDS using the two classifications were, respectively, 0.73 (95% CI, 0.65 to 0.81), 0.46 (95% CI, 0.32 to 0.61), and 0.63 (95% CI, 0.41 to 0.79). No single component of either index contributed to disagreement to an appreciably greater extent than other components. Baseline characteristics and outcomes were similar among patients who developed ARDS according to either classification. We conclude that NAECC and LISS classifications resulted in similar estimates of the incidence of ARDS in this clinical trial, though patients were frequently classified as having ARDS with only one model. These discordant classifications had no prognostic importance.

Pathophysiology and implications for treatment of acute respiratory distress syndrome

Acute respiratory distress syndrome is a complex group of signs and symptoms caused by direct or indirect lung injury. In spite of decades of research, it is still associated with a high mortality rate. Pathogenesis of this disease is related to alveolar endothelial and epithelial cell injury and associated release and sequestration of inflammatory mediators and cells, including cytokines and neutrophils, respectively. Pharmacologic interventions have been largely unsuccessful, and ventilation strategies to support oxygenation while limiting ventilator associated lung injury have not demonstrated any significant reductions in the mortality rate. However, novel therapies are in development, based on the knowledge of the pathologic processes of acute respiratory distress syndrome. In this article an overview of the disease process and mediator involvement is presented, followed by a review of pharmacologic and ventilation treatments currently in use or under study.

Acute lung injury and acute respiratory distress syndrome in sepsis and septic shock

Sepsis remains the leading cause of ARDS, and ARDS is still an often fatal condition. With our expanding knowledge of the pathobiologic mechanisms and the relationship between these two entities, early recognition, treatment, and prevention of sepsis may prevent or hasten recovery from ARDS. Understanding the biologic markers involved in the complex inflammatory response of sepsis and acute lung injury offers the possibility of future investigations to target treatment based on these mediators.

Relationship of admission plasma gelsolin levels to clinical outcomes in patients after major trauma

Actin-scavenging proteins, e.g., plasma gelsolin, counteract the pathophysiological consequences of actin leaked into the circulation from dying cells, but the capacity of this defense system can be overwhelmed by massive tissue injury. We examined the prognostic implications of plasma gelsolin levels obtained near the time of admission to our level I Trauma Unit on the subsequent clinical course in a group of patients with severe traumatic injuries. Blood samples were obtained from 13 patients shortly after major trauma and 11 healthy volunteers who served as the control group. Plasma gelsolin levels were assayed by quantitative Western blotting. Duration of mechanical ventilation, stay in the Trauma Intensive Care Unit, and development of acute respiratory distress syndrome (ARDS) were measured as clinical outcomes reflecting the complexity of the hospital course. Subsequently, we evaluated an additional 52 patients after major and minor trauma to extend our earlier observations. Plasma gelsolin concentrations were significantly lower in our 13 original patients compared with healthy controls. Levels below 250 mg/L (> 2 standard deviations below the mean of the control group) were associated with prolonged mechanical ventilation and a stay in the intensive care unit >/= 13 days. Both patients whose gelsolin level was < 100 mg/L in this first series developed ARDS. Including all 65 patients, 6 of the 10 patients who developed ARDS had admission gelsolin levels less than 250 mg/L, compared with only 7 of the 55 patients without ARDS (p = 0.0028). The mean gelsolin levels were 193 and 400 mg/L in patients with and without ARDS, respectively (p < 0.0001) and 398 mg/L in survivors versus 259 mg/L for patients who expired (p < 0.0001). Ten of the 13 patients (77%) with gelsolin levels at the time of admission more than 2 SD below the control mean had "bad outcomes," defined as mechanical ventilation for >/= 13 days in the Trauma Intensive Unit, ARDS, and/or death. Plasma gelsolin levels appear to be an early prognostic marker in patients experiencing major trauma. Whether circulating gelsolin serves a biologically vital function or is simply depleted after massive trauma cannot be determined from our study. The potential therapeutic benefits of infusions of recombinant human plasma gelsolin for patients in whom multiorgan dysfunction commonly follows a serious but self-limited insult have not yet been investigated.

Right heart catheterization in acute lung injury: an observational study

Right heart catheterization (RHC) is commonly used in the diagnosis and management of acute lung injury (ALI). However, controversy exists regarding RHC. We examined RHC use during the first 3 d of ALI in an observational study of 135 patients defined by American-European Consensus Conference criteria. Study parameters examined for association with RHC included the Acute Physiology and Chronic Health Evaluation (APACHE) III score, lung injury score (LIS), and 20 additional epidemiologic, clinical, and laboratory parameters. RHC was performed in 70 patients (52%) within the first 3 d of ALI. RHC was positively associated (p < 0.05) with a diagnosis of sepsis, APACHE III score, blood urea nitrogen (BUN), creatinine, net fluid balance, and positive end-expiratory pressure. RHC was negatively associated (p < 0.05) with mean arterial pressure (Pa) and PaO2/FIO2. Logistic regression identified four predictors for RHC placement: sepsis, PaO2/FIO2, BUN, and Pa. Initial right atrial and pulmonary artery occlusion pressure measurements demonstrated a moderately strong correlation (r = 0.72). Use of RHC was associated with a change in one or more therapeutic interventions (intravascular fluids, vasopressors, diuretics) in 78% of patients. In summary, patients receiving RHC during the first 3 d of ALI were more severely ill than those who did not receive RHC, and RHC was associated with a change in therapy in most patients.

Initial serum ferritin levels in patients with multiple trauma and the subsequent development of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) represents a catastrophic form of inflammatory lung injury that occurs unpredictably in some, but not all, at-risk patients. In this study, we investigated serum ferritin as a marker for ARDS development in a homogenous group of patients at-risk because of multiple trauma. We hypothesized that since ferritin synthesis is increased by proinflammatory cytokines, which are increased and implicated in ARDS, that ferritin levels would increase and that ferritin increases would correlate with the degree of inflammation and therefore the development of ARDS. We studied 42 patients (25 male, 17 female) who as a consequence of multiple trauma became at-risk for developing ARDS. Using the European/American Consensus definition for ARDS, 16 (38%) patients subsequently developed ARDS (11 male and five female). We found that initial serum ferritin levels correlated with the subsequent development of both ARDS (progression to ARDS, median = 638 ng/ml; (range, 70 to 4,500) versus nonprogression to ARDS = 185 ng/ml; range, 12 to 2,850) (p = 0.02, r = -0.27) and multiple organ failure (p < 0.05, r = 0.39). Using our previously established cutoff points for serum ferritin, the positive predictive value was 62% for men and 75% for women. Initial serum ferritin levels also correlated with a measurement of the degree of initial trauma injury, i.e., the injury severity score (ISS) (p < 0.05, r = 0.37). However, there was no correlation between serum ferritin levels and other markers of clinical injury, namely, lowest PaO2/FIO2 ratio (p = 0.67), days requiring ventilation (p = 0.09), or mortality (p = 0.42). A significant association existed between serum ferritin levels and products of endothelial activation, i.e., sE-selectin (p < 0.04, r = 0.37) and sICAM-1 (p < 0.01, r = 0.21). In the future, with the development of novel anti-inflammatory therapies, early identification of specific high-risk patients would allow the institution of these therapies and thereby increase the chances of reducing ARDS morbidity and mortality.

Crystalloids, colloids and kids: a review of paediatric burns in intensive care

This is a retrospective review of all burns patients admitted to a paediatric intensive care unit (PICU) over a 7 year period. Resuscitation fluid therapy and clinical course are presented. Ninety-eight new burns victims were admitted with a mortality rate of 10.2%, all in burns of greater than 25% body surface area (BSA). The incidence of ARDS was 20%, with an 18% mortality rate. Of 85 patients with burns greater than 5% BSA, 33 received the hospital-recommended colloid-based resuscitation formula, 46 received a combination of crystalloids and colloids and in 6 patients the resuscitation regimen was not able to be determined. The aetiology, age distribution, sex ratio, severity of burns and length of stay in hospital did not alter significantly over the study period. The number of burns admissions to PICU increased, as did their duration of intubation and ICU stay. The hospital-recommended resuscitation formula consistently underestimated the fluid volume required for adequate resuscitation. No statistically significant difference in adverse effects was found between the resuscitation groups. This study is unable to recommend a definitive approach to the fluid resuscitation of burns shock in paediatrics and the best approach is one of meticulous fluid resuscitation titrated on clinical effect.

Early predictive factors of survival in the acute respiratory distress syndrome. A multivariate analysis

To identify the potential impact of novel therapeutic approaches, we studied the early predictive factors of survival at the onset of acute respiratory distress syndrome (ARDS) in a 24-bed medical ICU of an academic tertiary care hospital. Over a 48-mo period, a total of 3,511 adult patients were admitted and 259 mechanically ventilated patients met ARDS criteria, as defined by American-European consensus conference, i.e., bilateral pulmonary infiltrates and PaO2/FIO2 lower than 200 without left atrial hypertension. These patients were randomly included in a developmental sample (177 patients) and a validation sample (82 patients). Demographic variables, hemodynamic and respiratory parameters, underlying diseases, as well as several severity scores (SAPS, SAPS-II, OSF) and Lung Injury Score (LIS) were collected. These variables were compared between survivors and nonsurvivors and entered into a stepwise logistic regression model to evaluate their independent prognostic roles. The overall mortality rate was 65%. SAPS-II, the severity of the underlying medical conditions, the oxygenation index (mean airway pressure x FIO2 x 100/PaO2), the length of mechanical ventilation prior to ARDS, the mechanism of lung injury, cirrhosis, and occurrence of right ventricular dysfunction were independently associated with an elevated risk of death. Model calibration was very good in the developmental and validation samples (p = 0.84 and p = 0.72, respectively), as was model discrimination (area under the ROC curves of 0.95 and 0.92, respectively). Thus, the prognosis of ARDS seems to be related to the triggering risk factor, the severity of the respiratory illness, and the occurrence of a right ventricle dysfunction, after adjustment for a general severity score.

Incidence of acute respiratory distress syndrome: a comparison of two definitions

OBJECTIVES

To determine the incidence and outcome of acute respiratory distress syndrome (ARDS) in children by comparing two commonly used definitions: the lung injury score and the American-European Consensus Conference definition. The causes and risk for developing ARDS were also studied.

METHODS

Part prospective and retrospective analysis of 8100 consecutive hospital admissions from 1 June 1995 to 1 April 1997.

RESULTS

Twenty one patients fulfilled the criteria for ARDS. Both definitions identified the same group of patients. The incidence was 2.8/1000 hospital admissions or 4.2% of paediatric intensive care unit admissions. The main causes were sepsis and pneumonia. Mortality was 13 of 21. Factors predicting death were a high admission paediatric risk of mortality (PRISM) score (30.38 v 18.75) and the presence of multiple organ dysfunction syndrome (92% v 25%).

CONCLUSION

Both definitions identified similar groups of patients. The incidence in this population was higher than that reported elsewhere, but mortality and cause were similar to those in developed countries. Poor outcome was associated with sepsis, a high admission PRISM score, and simultaneous occurrence of other organ dysfunction.

The 67gallium-transferrin pulmonary leak index in patients at risk for the acute respiratory distress syndrome

OBJECTIVE

To determine the occurrence and clinical importance of increased pulmonary microvascular permeability in patients at risk for acute respiratory distress syndrome (ARDS).

DESIGN

Prospective, cohort study.

SETTING

Medical and surgical intensive care unit (ICU) and department of nuclear medicine of a university hospital.

PATIENTS

Thirteen consecutive patients at risk for ARDS with sepsis (n = 4), multiple trauma (n = 3), hemorrhagic pancreatitis (n = 5), and near-drowning (n = 1), admitted into the ICU. All patients were intubated and mechanically ventilated in the course of the study.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The 67gallium-transferrin pulmonary leak index (PLI) (upper limit of normal in patients scheduled for major surgery 14.7 x 10(-3)/min) was measured within 24 hrs of admission. In addition, radiographic, gas exchange, and ventilatory variables allowing calculation of the Lung Injury Score, were obtained on the day of the PLI (day 0) and from days 1 to 7. Patients were followed until discharge or death in the ICU. No patient developed ARDS (Lung Injury Score of >2.5 in the absence of congestive heart failure) and all but four patients survived. The PLI (median [range]) was 18.5 (7.0 to 81.9) x 10(-3)/min and was supranormal in 8 of 13 patients (p < .001 vs. normal). The PLI correlated with the Simplified Acute Physiology Score (SAPS) II (r[s] = .79, p < .01) and was higher in nonsurvivors than in survivors (p < .05), with a tendency for a higher SAPS II in the nonsurvivors. On day 0, the chest radiographic score of alveolar abnormalities was 0 (0 to 4), indicating absence of radiographic abnormalities in most patients. Also, on day 0, the median PaO2/FIO2 ratio was 257 (range 119 to 460). The Lung Injury Score on day 0 was 1.0 (0 to 2.0), which is consistent with mild acute lung injury in all but one patient. In the course of time, the oxygenation ratio was lower and the Lung Injury Score was higher in nonsurvivors than in survivors, particularly for the Lung Injury Score on days 1 and 2. The PLI correlated directly with the Lung Injury Score on days 0 and 1. On day 0, the PLI correlated inversely with the oxygenation ratio. On the last evaluable day of the first ICU week, the PLI correlated directly with the Lung Injury Score and the positive end-expiratory pressure level. The duration of mechanical ventilation tended to be longer in patients with a supranormal PLI.

CONCLUSIONS

In this small population, 61% of patients at risk for ARDS and with only mild respiratory changes exhibited increased microvascular permeability in the lungs at ICU admission. Increased permeability may be an early marker of acute lung injury and its clinical features, and may be associated with a relatively complicated respiratory course during the first week after admission, even in the absence of progression to ARDS. Finally, increased pulmonary microvascular permeability may be associated with severe underlying disease and ultimate mortality in the ICU.